1. Field of Invention
The invention relates to an ink-jet printer for jetting ink on a recorded medium from an ink-jet head to form an image, and in particular, relates to an ink-jet printer which can detect that an ink jetting failure has occurred in the ink-jet head.
2. Description of Prior Art
Heretofore, a conventional ink-jet printer cannot automatically detect an ink jetting failure, such that when a user finds the omission (a so-called defect) of a printed image formed on a recorded medium, the user must determine that an ink jetting failure has occurred. When an ink jetting failure occurs, a user cleans an ink-jet head with a swab, etc., to solve the ink jetting failure. An ink-jet printer provided with a maintenance device for cleaning an ink jetted path in an ink-jet head has been recently developed. For the maintenance device, a purging device in which ink in the above ink jetted path is forcedly discharged together with bubbles and dust, and the nozzle face is wiped to remove the ink and dust around the nozzle, etc., has been devised. When an ink jetting failure occurs, the above ink-jet head failure can be solved by cleaning the above ink jetted path using the above maintenance device.
However, as a conventional type ink-jet printer cannot detect an ink jetting failure until a user finds the omission on a printed image formed on a recorded medium, a large quantity of printing error may be caused. A plan that when an ink jetting failure may occur, the above ink jetted path is cleaned by the maintenance device at a predetermined time, has also been devised. However, in this case, maintenance is required to be frequently executed sufficiently in advance. During maintenance, the printing operation is required to be interrupted and during purging and the like, ink is consumed. Therefore, in this case, valuable ink is consumed by frequent maintenance and the time required for printing is also extended.
The invention provides an ink-jet printer for enabling precisely and automatically detecting an ink jetting failure in an ink-jet head. In particular, the invention automatically solves an ink jetting failure when the ink jetting failure occurs, by automatically supplementing the ink supply when the ink supply decreases, and reducing the load related to processing.
A printer according to the invention is based upon an ink-jet printer provided with an ink tank for storing ink, an ink-jet head for jetting ink in the ink tank onto a recorded medium according to a driving signal, a detector for detecting the consumed quantity of ink in the ink tank, a calculation unit for calculating the consumed quantity of ink in the ink tank according to a driving signal, and a determination unit for comparing the consumed quantity of ink calculated by the calculation unit and that detected by the detector and determining that an ink jetting failure has occurred in the ink-jet head if difference between both exceeds predetermined quantity.
In the invention as described above, an ink-jet head jets ink stored in an ink tank onto a recorded medium according to a driving signal. The detector detects the consumed quantity of ink in the ink tank. As an ink-jet head jets ink according to a driving signal, the consumed quantity of ink in the ink tank normally has a relation to the driving signal. The calculation unit calculates the consumed quantity of ink in the ink tank according to the driving signal. The determination unit compares the consumed quantity of ink calculated by the calculation unit and that detected by the detector and determines that an ink jetting failure has occurred in the ink-jet head if difference between both exceeds a predetermined quantity. That is, as ink is not jetted according to a driving signal when an ink jetting failure occurs, the difference between the consumed quantity of each ink calculated and detected is determined. That is, if an ink jetting failure continues for a fixed period, the counted value of the consumed quantity gradually comes off. When such a situation occurs, the determination unit determines that an ink jetting failure has occurred.
Therefore, according to the invention, an ink jetting failure in an ink-jet head can be precisely and automatically detected. According to the detection, a warning can be given and printing can be also halted. Therefore, even if a user fails to find the ink jetting failure, a large quantity of printing error can be satisfactorily prevented from occurring.
If maintenance is executed as necessary based upon the result of the determination by the determination unit according to the invention, the frequency of maintenance to be executed is appropriately set, and ink and printing time can be satisfactorily prevented from being wasted. As the time to execute maintenance according to the result of the determination, the time of maintenance may be also set and stored as the time when an ink jetting failure occurs, a total quantity of ink is jetted, a total time that an inkjet head is driven, and the like, before an ink jetting failure occurs since the last maintenance. The time of maintenance may be also set to a time immediately before the jetted quantity and the driven time occurs. In the case of the latter, the occurrence of an ink jetting failure can be prevented beforehand and the occurrence of a printing error can be more satisfactorily inhibited.
Further, the invention is characterized in that a maintenance unit for cleaning an ink jetted path in an ink-jet head and a maintenance controller for cleaning the ink jetted path by the maintenance unit when the above determination unit determines that an ink jetting failure occurs, are further provided.
According to the invention, when the determination unit determines that an ink jetting failure occurs, the maintenance controller instructs the maintenance unit to clean an ink jetted path in an ink-jet head. Therefore, according to the invention, when an ink jetting failure occurs, it can be automatically solved. Also, according to the invention, as maintenance (cleaning an ink jetted path) is executed when an ink jetting failure occurs, the frequency in which maintenance is executed can be minimized. Therefore, ink and printing time can be prevented from being wasted.
Further, the invention is characterized in that the above detector can detect when ink in an ink tank decreases and ink is required to be supplemented. An ink supply unit for supplying a predetermined quantity of ink in an ink tank and supply controller for instructing the above ink supply unit to supply ink when the detector detects that ink is required to be supplemented, may be further provided. When the detector detects that ink is required to be supplemented, the supply controller supplies a predetermined quantity of ink to an ink tank via the ink supply unit. Therefore, according to the invention, ink can be automatically supplemented when the ink decreases.
The ink supply unit according to the invention supplies a predetermined quantity of ink to an ink tank. Therefore, if the detector detects that ink is required to be supplemented, the ink supply unit supplies ink and afterward, the detector detects that ink is required to be supplemented again, the consumed quantity of ink is the above predetermined quantity. Therefore, the detector according to the invention can detect the consumed quantity of ink even if the detector only detects that ink is required to be supplemented. Therefore, in this case, the structure of the ink-jet printer can be extremely simplified and the manufacturing cost can be reduced satisfactorily.
Further, the invention is characterized in that the detector can detect that ink in an ink tank decreases up to a first reference value and ink in the ink tank decreases up to a second reference value different from the first reference value. Therefore, when the quantity of ink in an ink tank is between both reference values, the consumed quantity of ink can be readily detected. In this case, the consumed quantity of ink in a short period can be detected, compared with a case that the detector only detects that ink is required to be supplemented. Therefore, the consumed quantity of ink calculated by the calculation unit may also correspond to a short period. Therefore, according to the invention, the load related to calculation processing by the calculation unit can be reduced. In the invention, the supplied quantity of ink may be arbitrary.